US2429722A

US2429722A - Circuit breaker

Info

Publication number: US2429722A
Application number: US345264A
Authority: US
Inventors: Oliver S Jennings
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1940-07-13
Filing date: 1940-07-13
Publication date: 1947-10-28
Anticipated expiration: 1964-10-28

Description

Oct. 28, 1947. o. 5. JENNINGS CIRCUIT BREAKER 0 4 9 1 5 l V. 1 H J d e l i F 4 Sheets-Sheet l INVENTOR 'OZI'UIPI'gYclWfiiWS a B Z moan:

WITNESSES: 'JW

Oct. 28, 1947. o. 5. JENNINGS 2,429,722

0 IRCU IT BREAKER 4 Sheets-Sheet 2 Filed July 115, 1940 wmursszs: 77 198 M JNVENTOR Oliverfidzwkys.

- Oct. 28, 1947. o. 5. JENNINGS 2,429,722

CIRCUIT BREAKER Filed July 13, 19 40 4 Sheets-Sheet 3 M .1 If Y k; "I a Q WITNESSES: INVENTOR 47% Olive/- 5. v/yyjys I MWM Oct. 28, 1947. o. 5. JENNINGS CIRCUIT BREAKER Filed July 13, 1940 4 Sheets-Sheet 4 i lll INVENTOR dive/ 5. Jsllll fys \H h m d r w m 7/4/7 nW NM. WNW

Patented Oct. 28, 1947 CIRCUIT BREAKER Oliver S. Jennings, Pittsburgh, Pa., asslgnor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application July 13, 1940, Serial No. 345,264

25 Claims. 1

The invention relates to circuit interrupters, and more particularly to manually and automatically operable low voltage circuit breakers for controlling lighting and other small and moderate power electric circuits;

An object of the invention is the provision of an improved circuit breaker of the class described which is compact and light in weight, accurate and reliable in operation, and inexpensive to manufacture.

Another object of the invention is the provision of an improved circuit breaker in which all parts thereof are removably mounted in a novel manner in a two-part separable enclosing housing of insulating material without the use of any frame other than the enclosure and withating mechanism and separate trip device, both supported in recesses and surfaces provided in a two-part housing of molded insulating material with the parts and surfaces disposed so that the reactions on the parts cause'them to naturally seat against fixed surfaces in such a manner as to insure substantially constant performance and accuracy of operation despite the degree of looseness of fit of the parts in the housing.

Another object of the invention is the provision of a circuit breaker embodying an opensided casing having recesses and surfaces for receiving and supporting the contact means and operating means and having additional recesses and surfaces for receiving and supporting either a combined magnetically and thermally responsive trip device, or a thermally responsive trip device, or a magnetically responsive trip device, the parts being removably mounted through the open side of the casing and retained in mounted position by a second casing member removably mounted on the open side of the casing, without any of the parts being positively fastened to the casing sections.

Another object of the invention is the provision of a. circuit breaker embodying an improved thermally and magnetically responsive trip de- 2 vice in which the thermally responsive bimetal trip element normally opposes tripping or release of the breaker mechanism, the construction of the trip device being such that bimetal trip elements of different stiffness or thickness may be substituted without affecting the operation of the electromagnetic trip means.

Another object of the invention is the provision of a thermally and magnetically controlled circuit breaker which provides a greater time delay action for a predetermined range of heavy overloads than is obtainable by conventional circuit breaker constructions.

The novel features that are considered characteristic of the invention are set forth in particular in the appended claims. The invention itself, however, both as to structure and operation together with additional objects and advantages thereof will be best understood from the following detailed description of several embodiments thereof when read in conjunction with the accompanying drawings, in which:

Figure 1 is a side elevational view, partly in section, of a circuit breaker constructed in accordance with the invention, one section of the two-part insulating housing having been removed to more clearly illustrate the invention, the breaker mechanism parts being shown in the circuit closed position;

Fig. 2 is a transverse sectional view of the complete breaker taken substantially along the line 11-11 of Fig. 1 and looking in the direction of the arrows;

Fig. 3 is a side elevational view of the breaker, similar to Fig. 1, showing the position of the parts an instant after tripping of the breaker;

Fig. 4 is a transverse sectional view of the complete breaker taken substantially along the line IV-IV of Fig. 3 and looking in the direction of the arrows;

Fig. 5 is a side elevational view of one part of the two-part molded insulating housing of the breaker;

Fig. 6 is a side elevational view of the removable side part of the housing showing the interior side thereof;

Fig. 7 is a fragmentary view of the circuit breaker with the side section of the housing removed showing a modified form of trip device;

Fig. 8 is a fragmentary view of the circuit breaker with the side of the housing section removed showing a thermally responsive trip device in mounted position in the casing in place of the combined magnetically and thermally responsive trip device shown in Fig. 1;

of the arrows, both sections of the housing being shown; and

Fig. 11 is a fragmentary sectional view of the breaker taken substantially on the line Xi-XI of Fig. 1 and looking in the direction of the arrows, both sections 01' the housing being shown.

My prior Patent 2,190,517, issued February 13, 1940, and assigned to the assignee of the present invention discloses a thermal circuit breaker in which the movable parts are removably supported on pivot pins in a two-part separable insulating casing. The present invention is distinguished from the aforesaid patent in a number of respects including the following: The present invention provides an improved circuit breaker operating mechanism and improved trip device which are separately mounted in recesses and surfaces provided in the two-part insulating casing with the parts and surfaces disposed so that the reactions on the parts cause them to naturally seat against fixed surfaces in such a way as to insure substantially constant performance and accuracy of operation of the breaker despite the degree of looseness of fit of the parts in the housing. The recesses and surfaces of the housing are arranged to receive and support either a combined magnetic and thermal trip device, or a thermal trip device, or a magnetic trip device, for use with the same mechanism. All parts including the terminals are removably supported without being positively fastened to the housing. In my Patent 2,190,517 only a single type of bimetal trip element can be used and this element is carried by the movable contact arm, and the terminals are positively fastened to the housing by screw fastenings.

In accordance with another of its phases, the present invention constitutes a further development of the invention disclosed and claimed in my copending application Serial No. 339,466, flied June 8, 1940, now Patent 2,329,053, issued September 7, 1943, and assigned to the assignee of the present invention. One embodiment of the trip device of the present invention is generally similar to that disclosed in the aforesaid copending application but is distinguished therefrom by the provision of a resilient means between the bimetal element and the latch whereby the operation of the electromagnetic trip means is independent of the thickness or stiffness of the bimetal element so that bimetal elements of different thickness or stiffness may be substituted without affecting the operation of the electromagnetic trip means. Another distinguishing feature of the present invention over the aforesaid copending application with reference to one form of the trip device is in the provision of a double armature with the armature sections separated by a low resistance conducting member whereby a greater time delay action is obtained in a predetermined range of overload currents.

Referring to Figs. 1-6 of the drawings, the circult breaker comprises in general a twopart separable housing |5 of molded insulating material, a stationary contact IT, a cooperating movable contact 9 carried by a switch arm 2|, an operating mechanism indicated generally at 23, a current responsive trip device indicated generally at 25 and a pair of

terminals

21 and 29 for connecting the breaker in an electrical circuit.

The housing H5 is adapted to enclose all of the parts of the circuit breaker mechanism other than the operating end of the manually operable operating lever and the terminal ends of the terminals, and the housing comprises two separable sections or parts 3| and 33 having the division plane or Joint between them disposed substantially parallel to the plane of movement of the switch arm 2|. The housing sections 3| and 33 serve as the frame for the breaker and are molded to provide various recesses and surfaces for removably receiving and supporting all of the parts, as will be hereinafter described, whereby the parts are slidably received through the open side of the housing section 3| when the sections are separated and are retained in mounted position when the housing sections are assembled, without any of the parts being positively fastened to the housing.

The housing section 3| has one solid side wall 35,

end walls

31 and 39, a bottom wall 4|, and a front wall 43 (Figs. 1 and 5). The front wall 43 is provided with an elongated notch 45 and well 41 both open at the open side of the housing section for accommodating the operating end and handle of the manual operating lever of the breaker. The front wall 43 of the housing section 3| is also provided with a pair of

projections

49 and 5| for limiting movement of the operating lever, and each projection is provided with a slot 53 for receiving and fitting the ends of an arcuate closure projection formed on the inner surface of the other housing section 33. The bottom wall 4| of the housing section 3| has an opening 55 formed therein adjacent the stationary and movable contacts of the breaker for venting the arc gases and this opening is bounded by a slot 51 on three sides thereof, the opening 55 and slot 51 being open at the open side of the housing section 3|. The slot 5'! is adapted to slidably receive and support a bottom baffle plate of an arc extinguisher which will be hereinafter described.

The opposite ends of the housing section 3| are formed to provide niches 59 and Bi which are open at the end, front, and open side of the housing section 3| for providing access to the terminal ends of the terminals 2'! and 29 of the breaker. The upper end wall 31 of the housing section is provided with a recess 63 open at the front and open side of the housing section for accommodating a terminal screw 65 which is threaded in an opening in the terminal end of the upper terminal 27 to provide a means for connecting this terminal of the breaker to an electrical circuit. An angle shaped transverse slot 9! is formed in the upper end wall 31 of the housing section 3i and this slot opens at its upper end into the niche 59 and at its lower end into the main chamber of the housing section 3|. The slot 61 is open at the open side of the housing section for slidably receiving the upper terminal 21, the walls of the slot serving to support the terminal 21 in mounted position.

The lower end wall 39 of the housing section 3| is formed to provide a recess H which is open at the front and open side of the housing section 3| for accommodating a terminal screw 13 which is threaded in an opening provided in the lower terminal 29 for connecting this terminal to an electrical circuit. The recess opens at 12 (Fig. 5) into a chamber 15 formed in the lower end of the housing section 3| for accommodating an electromagnetic trip means which will be hereinafter described.

The housing section 33 forms a closure for the open side of the housing section 3I and is formed as a generally flat plate having recesses and pro- Jections on its inner surface for aiding in supporting certain parts of the circuit breaker. The housing sections 3i and 33 are adapted to be secured together in assembled relation by three bolts 11 (Fig. 2) which extend through aligned openings 18 (Figs. 2. and 6) provided therefor adjacent three corners of each housing section. The heads of the bolts are adapted to seat in counter-sunk holes in the housing section 3I and the ends of the bolts are threaded to engage nuts 8I (Fig. 2) disposed in counter-sunk holes provided therefor in the outer surface of the closure section 33.

The upper terminal 21 comprises a flat strip of conducting material bent at right angles at several points so that it has a step shape, and the stationary contact I1 is rigidly secured to the lower end of this terminal. The lower terminal 28 comprises a substantially rectangular flat plate of conducting material having an ear 83 on one side which is bent at a right angleto the terminal. The other side of the terminal 28 has a projection 88 formed integral therewith (Figs. 4 and which-is adapted to fit snugly in a rectangular recess 81 (Fig. 5) provided therefor in the wall 38 of the housing section 3I. The cover section 33 of the housing is provided with a rectangular recess 88 (Figs. 6 and 10) which fits the ear 83 of the terminal 28 when the casing sections are assembled to securely retain the terminal in mounted position. The lower wall 38 of the housing section 3| is also provided with a slot 8| (Figs. 1 and 5) into which the upper edge of the terminal 28 projects as seen in Figs. 1 and 10.

The terminal 21 is removably inserted in the housing section 3I by sliding the terminal edgewise into its slot 81 through the open side, and is securely retained in mounted position when the cover section 33 of the housing is secured in assembled position on the housing section 3I. Similarly, the lower terminal 28 is inserted in the recesses and slots provided therefor in the lower end of the housing section 3|, and is securely retained in mounted position by the cover section 33 of the housing-when the housing sec-- tions are assembled.

The are extinguishing device comprises a pair or U-shaped elements 83 (Figs. 1 and 2) of magnetic material which are assembled between side plates 88 of arc resistant insulating material. The side wall 38 of the housing section H is provided with a pair of rectangular recesses 81 (Fig. 5) which are adapted to receive and fit one end of the U-shaped magnetic elements 83 when the arc extinguishing device is assembled in the housing. The legs ofthe U-shaped magnetic elements 83 and the insulating side plates 38 are disposed on opposite sides of the path of movement of the movable contact I8. A baffle plate 88 is removably mounted in the slot 81 provided in the housing section 3I. by sliding the plate edgewise into the slot 81. The plate 88 engages the back edges of the insulating side plates 88 and thus aids in supporting the side plates, and the baffle plate 88 is provided with a plurality of openings I8I to allow the escape of the arc gases through the back of the housing. A plate I83 of arc resisting insulating material is removably mounted in an L-shaped slot I88 (Fig. 5) provided in the upper end wall 31 and side wall 38 of the housing section 3I for projecting the operating mechanism from the arc. The plate I83 is removably inserted in the housing section 3I by sliding the same edgewise into the slot I88 and is retained in mounted position by the cover section 33 of the housing. Another plate I81 of are resistant insulating material is removably mounted in an L-shaped slot I88 (Fig. 5) formed in the upper end wall 31 and the side wall 38 of the housing section 3 I. The plate I81 is disposed immediately above the arc extinguisher and serves to protect this portion or the housing from damage by the are as the arc is moved by the magnetic elements 83 towards the bottom wall of the housing. The insulating side plates 88 of the arc extinguisher are retained in mounted position when the housing sections are assembled by reason of the fact that they are held between the side walls of the housing I8 and the legs of the U-shaped magnetic elements 83. The upper right-hand corners of the insulating side plates 88 bear against the plate I83 and the edges of the plates parallel to the bottom wall of the housing bear against the baffle plate 88, so that the plates are securely retained in proper position within the housing. The are extinguishing structure and the plates I81 and I83 are removably mounted in the housing section 3| by sliding the same into the recesses and slots provided, therefor through the open side of the housing section 3i. The cover sction 33 of the housing is provided with a slot III which fits the side edge of the baffle plate 88.

The operating means of the circuit breaker comprises a releasable supporting member I I3 for pivotally supporting the switch arm 2|, a manually operable operating lever I I8, and an overcenter spring II1 connected in tension between the switch arm 2I and a part of the operating lever The releasable supporting member II3'comprises a yoke-shaped lever or cradle having spaced legs II8 (Fig. 2) which are Joined at their upper ends by a cross piece I28 and at their lower ends by a latch element I2I which cooperates with a movable latch of the trip device. The cross piece I 28 is formed integral with the spaced legs II8 of the releasable member, and the latch element I2I is secured between the lower ends of the legs of the lever by means of retaining pins or rivets I23. The legs of the releasable member II3 are generally V-shaped in side elevation and the switch arm 2I is pivotally engaged at one end in the apex of the releasable member II3. The switch arm 2I is bifurcated at one end to form spaced legs I 28 and the ends oi the legs are notched as indicated at I21 in Fig. 2 for pivotally engaging the legs of the releasable member I I3 at the apex thereof, as shown in Figs. 1 and 2. The releasable member II3 is mounted for pivotal movement by a pivot pin I28, the ends of which are supported in cylindrical bearing recesses I3I and I33 (Figs. 2, 5 and 6) provided therefor in the housing sections 3I and 33, respectively, whereby the releasable member is removably mounted in the insulating housing. The releasable member II3 is always biased in a counterclockwise direction about its pivot I28 as viewed in Fig. 1 by the overcenter spring H1, and is adapted to be restrained in the normal position shown in Fig. i by the latch of the trip device which engages the latch element I2I of the releasable member.

The manually operable operating lever H5 is disposed for pivotal movement within the housing in a shallow V-shaped recess I35 formed in the side wall 35 of the housing section 3|. The operating lever is rounded at its inner end and this end is pivotally supported in the rounded bottom of the V-shaped recess I35 as best shown in Fig. 2. The outer end of the operating lever H is offset and the offset portion extends out through the notch 45 of the housing section 3| and is provided with an operating handle I31 which is rigidly secured to the outer oflset end of the lever. The cover section 33 of the housing is provided with an arcuate projection I28 having an arcuate portion I30 which is adapted to underlie the side edge of the notch 45 of the housing section 3i and cooperate therewith to form a closure for the handle opening when the housing sections are assembled as shown in Fig. 2. The overlap relation between the portion I30 and the side edge of the arcuate portion 45 provides a tortuous path to minimize the danger of flame and hot gases escaping through the handle opening. A stud I39 is rigidly secured to the operating lever II5 adjacent the ofiset outer end thereof and this stud projects laterally from the lever and carries a roller MI at its free end. The cover section 33 of the housing is provided with an arcuate slot I43 (Figs. 2 and 6) disposed concentric with the pivot axis of the operating lever for receiving the roller MI. The roller MI bears against the bearing surface formed by the bottom wall I45 of the arcuate slot 143. The roller is adapted to be moved back and forth along the bearing surface I 45 as the operating lever H5 is moved back and forth between open and closed circuit position. It will thus be seen that the operating lever is pivotally supported in two spaced bearings one comprising the rounded inner end of the V-shaped recess I35 of the housing section 3! and the other comprising the arcuate bearing surface I45 formed in the cover section 33 of the housing.

The overcenter spring H1 is disposed between the legs I25 of the bifurcated end of the switch arm 2| and has one end connected to the switch arm 2i by being hooked into an opening I41 provided in the switch arm. The other end of the overcenter spring is anchored in a notch I49 provided in the stud I39 midway between the ends of the stud. The spring II1 serves to retain the switch arm 2i in pivotal engagement with the su porting member H3, and the operating lever I I5 in pivotal engagement with the bearings. The pivot bearings of the pivoted operating lever H5 and the pivotedswitch arm 2I and the pivoted support member I I3 are spaced on opposite sides of the overcenter spring II1 as shown in Fig. 2, thereby providing a. well balanced construction and insuring smooth and accurate operation oi the mechanism.

The operating lever I I5 is moved in an upward direction to effect closing of the circuit breaker. As soon as the line of action of the overcenter spring H1 is moved above the pivot axis of the switch arm 2|, the spring acts to move the switch arm N to closed circuit position with a snap action. The operating lever II 5 is moved in a downward direction to open the circuit breaker and as soon as the line of action of the overcenter spring I I1 passes below the pivot axis of the switch arm 2 I, the switch arm is thereby caused to move to open circuit position with a snap action. The circuit breaker is adapted to be automatically opened in response to overload conditions by the trip device 25 which will be hereinafter described. The operation of the trip device in response to an overload effects release or the releasable supporting member H3, and the overcenter spring II1 moves the supporting member in a clockwise direction or upward direction about its pivot axis I29 thereby shifting the pivot axis of the switch arm 2I above the line of action of the overcenter spring H1 and thus causing movement of the switch arm 2i to an open circuit position with a snap action irrespective of the position of the operating lever H5. Before the breaker can be manually reclosed following a tripping operation. it is necessary to reset the releasable supporting member II3 to its normal latched position. The mechanism is reset following a tripping operation by manually moving the operating lever I I5 downwardly to open circuit position. The operating lever is provided with a resetting projection II6 (Fig. 1) which projects laterally from the lever and is adapted to engage and move the releasable member H3 in a clockwise direction or downward direction back to its normal latched position ,upon downward movement of the operating lever H5 to open position. The breaker may be manually closed following resetting in the manner previously described for the closing operation.

The U-shaped magnetic elements 93 of the are extinguisher set up a magnetic field upon opening of the circuit which acts to elongate and move the arc toward the bai'fle plate IIII, and the arc is quickly extinguished by the cooling and deionization of the arc gases in a well known manner and by the attenuation of the arc.

The trip device 25 is removably mounted in the lower portion of the housing section II without any part thereof being positively fastened to either of the housing sections. The trip device comprises, in general, a pivoted latch lever I5I controlled by an eiectromagnet I53 and by a. thermally responsive bimetal element I55. The electromagnet comprises a U-shaped core I51 of magnetic material, and a double armature comprising two armature-sections I59 and lil of magnetic material secured to the opposite sides of the pivoted latch lever I5I, and an energizing winding I63 which is wound upon the long leg of the core I51.

The latch lever I5I is preferably formed of a single piece of low resistance conducting material such as copper and has a yoke-shaped portion providing spaced legs which straddle and are pivoted to the longer leg of the magnet core I51 by means of a pivot pin I95, as shown in Figs. 1 and 11. The latch lever has a latch element or projection I61 struck out therefrom which is adapted to engage the latch element I2I of the releasable member II3 to normally hold the releasable member in operative position. The latching surfaces of the latch elements III and I61 are preferably disposed perpendicular to a line projected from their point of engagement to the center of the pivot pin I65 so that the overcenter spring II1 of the breaker mechanism does not bias the latch lever I5I in either direction.

A tension spring I69 is anchored at one end to a-projection ill of the latch lever I5I, the coils of the other end of the spring engage the threads of an adjusting screw I13 whereby the pull of the spring may be adjusted to thereby vary the trip characteristic of the device. The spring I 59 acts to bias the latch lever I5I to the unlatched or released position and the strength of the spring is preferably more than sufficient to overcome the latch load and release the supporting lever II 3 except when the member is restrained by the bimetal element. The lower end of the biasing spring I39 projects laterally into a vertical slot I10 provided in the side wall 35 of the housing section 3I so that the spring is prevented from turning with the screw I13. The lower end wall 39 of the housing section 3| is provided with an opening I13 opposite the head of the screw I13 to permit adjustment of the screw from outside the housing. I

The thermally responsive bimetal element I55 comprises a flat strip of bimetallic material bent in a U shape and secured at one end to a bracket I15 of conducting material. The bimetal element is mounted in the housing so that it is free and engages the underside of the free end of the latch lever I and is insulated therefrom by an insulating button I11 secured to the free end of the latch lever I5I.

The bimetal element I55 normally assumes a position shown in Fig. 1 and acts to oppose movement of the latch lever to the unlatched position and normally restrains the latch lever in latching position. When the bimetal element is heated a predetermined amount, it is free and flexes or is moved in a downward direction, that is, away from the operating mechanism to permit movement of the latch lever I5I toward the unlatched position.

The energizing winding I33 of the electromagnet and the bimetal element I55 are electrically connected in series with the contacts I1 and I3 of the circuit breaker so as to be traversed by the current flowing in the circuit controlled by the breaker. The free end of the bimetal element is electrically connected to the pivoted supporting member II3 by a flexible shunted conductor I13. The pivoted supporting member H3 and the switch arm 2| are of conducting material and being in'engagement effect electrical connection of the movable contact I9 to the flexible shunt conductor I19.

One end of the energizing winding I33 of the electromagnet is brazed to the ear 33 of the lower terminal 29, and the other end of the winding I33 is brazed to the bracket I15 of the bimetal element I55. The electrical circuit through the breaker extends from the upper terminal 21 through the stationary contact I1, the movable contact I3, switch arm 2|, pivoted supporting lever I I3, flexible shunt conductor I19, bimetal element I 55, and energizing winding I33 to the lower terminal 29.

The energizing winding I63 of the electromagnet is relatively still so that it acts to support the bimetal element I55 and the terminal 29 in approximately correct position for insertion in the housing and so that the electromagnet I53,

the bimetal element I55 and the terminal 23 are, in effect, a unit, although the bimetal element and the terminal may be moved relative to the electromagnet by bending the ends of the energizing winding I63.

The unit comprising the electromagnet I53, the bimetal element I55 and the terminal 29 is fitted in the housing section 3| by sliding the same sidewise through the open side of the casing in suitable recesses provided for the unit. The electromagnet is adapted to be disposed in the chamber 15 of the housing section 3I The long leg of the magnet core I51 is engaged by surfaces I3I, I33, I85 and I81 of the bottom wall of the housing section 3I and the short leg of the magnet core is engaged by the surface 10 I33 formed in the lower end wall 33 of the housing section and also by a surface I3I of a proiection I33 formed in the housing section 3|. One side of the magnet core I51 is engaged by the surface I33 (Figs. 4 and 5) or the housing section 3I, and the other side of the magnet core is engaged by projections I30 and I92 (Fig. 6)

formed on the inner surface of the cover section 33 of the housing when the housing sections are assembled thereby preventing sidewise displacement of the electromagnet in the housing. The ends of the pivot pin I35 fit in cylindrical bearing recesses I35 and I31 (Figs. 4, 5 and 6) formed in the housing sections 3| and 33, respectively. The housing sections 3I and 33 are each provided with complementary dished recesses I33 and I33 for accommodating the sides of the energizing winding I33.

The bracket I15 of the bimetal element I fits in a slot 2M (Figs. 2, 5 and 10) provided in the side wall 35 of the housing section 3I, and one side of the bracket is bent at right angles, as indicated at 203, and this bent side fits in a recess 235 (Fig. 5) provided therefor in the side surface of the lower end wall 39 of the housing section H. The surface of the bracket I15 which faces the operating means is engaged by the upper wall of the slot MI and by the surface 231 of the projection I93 formed in the housing section 3I and the opposite surface of the bracket is engaged by the other wall of the slot 20L From the foregoing it will be seen that the stationary core I51 of the electromagnet I53 and the bracket I15 to which the bimetal elementis secured are adapted to be slidably received in the recesses provided therefor by sliding these elements sidewise through the open side of the housing section 3| into the recesses. The stationary core of the electromagnet and the bracket of the bimetal element are maintained in proper position by the engaging and supporting surface provided therefor in thehousing section 3|. The stationary core I51 of the electromagnet is prevented from being moved in a vertical direction by the surfaces I3I and I31 and by the engagement of the pivot pin I in the bearing recesses I35 and I91. Counterclockwise or clockwise twisting or turning of the magnet core is prevented by reason of the engagement of the surfaces I33 and I35 with one-leg of the magnet core and by the surfaces I9I and I89 which engage the other leg of the magnet core. Similarly, the bracket I15 of the bimetal element is prevented from being moved vertically or from being twisted in a clockwise or counterclockwise direction by reason of the engagement thereof in the notch MI and in the recess 205. The lower surface of the projection I93 also prevents vertical or twisting movement of the bimetal bracket. It will also be noted that the reaction forces on the various elements of the circuit breaker mechanism and trip device cause them to naturally seat against the fixed surfaces provided therefor in the housing, thereby providing substantially constant performance irrespective of the degree of tightness or looseness of fit of the elements in the housing. For example, the reaction on the latch lever I5I caused by the overcenter spring II1 causes the ends of the pivot pin I35 to always engage the front side of the bearing recesses I95 and I31 and also causes the magnet core I51 to more firmly seat against the surfaces I9I and I35. Similarly, the reaction force on the bimetal element I55 causes its bracket I15 to seat against the fixed surface of the lower wall of the slot 2M and against the surface 201 of the projection I". It should also be noted that the reaction force of the spring II! is transmitted through switch arm 2I and supporting member H3 to the pivot pin I29 and thereby biases it to bear against the right-hand side (when viewed as in Fig. 1) of the recesses I3I and I33. The fact that the recesses I3I and I33 and the holes of the member II3 are cylindrical results in the member II! being held by the bias thereon in the same position vertically. This construction together with the similar construction and bias on pivot pin I65 give a constant amount of overlap between the latch elements Ill and I61. This gives the advantage that the calibration of the breaker remains constant even though there may be looseness in the mounting of the parts and wear of the bearing surfaces.

All of the aforementioned parts of the circuit breaker, including the terminals, the operating means, and the trip device, are fitted into the recesses provided therefor through the open side of the housing section Si by sliding the elements sidewise into their recesses, and all of the parts are retained in mounted position when the housing sections 3| and 33 are assembled without any of the parts of the circuit breaker being positively fastened to either of the housing sections. To remove the circuit breaker parts it is only necessary to remove the cover section 33 of the housing and slide the parts sidewise out of the housing section 3i through the open side thereof.

The ,manual operation of the circuit breaker has previously been described. The automatic operation of the breaker onoverload is briefly as follows: As the current of the circuit increases above the normal rated current, the bimetallic element I55 is heated thereby and gradually decreases its restraining force which opposes release of the latch lever II. At the same time the pull or unlatching force of the electromagnet I53 increases with the increase in current. The latch lever I5I is moved to the unlatched position as soon as the combined force of the electromagnet I53 and spring IE8 is sufllcient to overcome the resilient opposing force of the bimetal element I55. The bimetal element I55 introduces a time delay action between the occurrence of the overload and the tripping or release of the circuit breaker mechanism up to a predetermined current value, for example, about 1000% of the rated current, Upon overload currents in excess of this predetermined magnitude the electromagnet I53 exerts sufilcient pull to effect substantially instantaneous tripping of the circuit breaker irrespective of the opposing force of the bimetal element I55, that is, even though the bimetal element may not have been heated a substantial amount. The time delay action introduced by the bimetal element in the range of overloads below the predetermined instantaneous tripping value varies inversely with the magnitude of the current, the time delay being greatest for light overloads and gradually decreasing as the value of the current increases. The arrangement of the parts of the trip device are such that the device operates to trip or release the breaker mechanism faster, that is, with shorter time delay in the intermediate'range of overload currents than conventional circuit breakers havin a bimetal trip element and an electromagnet which act independently to trip the breaker. This result is obtained principally by reason of the fact that the electromagnet I exerts an unlatching force at all times when it is energized which force increases with the increase in current while the bimetal element merely resiliently opposes unlatching with a force which decreases as the element is heated by the current. The unlatching force of the electromagnet becomes appreciable in the intermediate range of overload currents. As a result less heating of the bimetal element is required to cause unlatching than if the force of the electromagnet were not present. The provision of the double armature comprising the two sections I51 and Ill separated by the low resistance conducting material of the latch lever I5I tends to increase the time delay action to a certain extent in the case of heavy overloads less than the predetermined magnitude, that is, less than short circuit magnitude by reason of the fact that the magnetic flux in passing through the upper armature traverses the low resistance conducting material of the latch lever III and thus sets up eddy currents which tend to reduce the magnetic flux and delay the time of its maximum value. The pulls of the two armatures are, therefore, out of phase. This has the effect of delaying the time of maximum pull and reducing the value of maximum pull. There will be little, if any, eilect of the eddy currents for lower magnitude overloads until the iron of the lower armature I59 becomes saturated. From this point on the upper armature I5I comes into action more strongly but somewhat held back by the counter flux produced by the eddy currents. This construction allows heavy overloads to exist for a slightly longer time without tripping the breaker than in the case of a single armature. On short circuit, however, both armatures become saturated and the eddy currents are ineffective to delay tripping of the breaker. This feature is of particular advantage in connection with the lighting of tungsten lamp loads as it enables the lighting of a greater number of tungsten lamps withouthtripping the breaker on the initial current rus An important feature of the present invention is the provision of a circuit breaker construction in which several different types of trip devices may be substituted for controlling the same mechanism, and can be removably mounted in the same housing. For this purpose the housing of the circuit breaker is provided with recesses and surfaces such as to receive and support either a combined magnetically and thermally responsive trip device such as shown in Fig. 1 and described in connection therewith, or a pure thermally responsive trip device as shown in Fig. 8, or a magnetically responsive trip device as shown in Fig. 9. This is a particularly desirable feature since it enables a complete line of circuit breakers to be manufactured using a single molded housing construction and the same type of mechanism, thereby materially reducing the cost of the circuit breakers and simplifying the stocking of parts.

Fig. 8 shows the circuit breaker equipped with a thermally responsive trip device comprising a bimetal element 2| I, the free end of which forms a latch for engaging the latch element III of the releasable support lever III. The housing construction, the upper terminal, the contact means, the operating means and the arc extinguishing structure are all of identical construction to that shown in Figs. 1-6 and described in connection therewith, and the same reference characters are used to designate the identical 13 parts. The thermally responsive bimetal trip element 2 comprises a flat strip of bimetallic material bent in a U-shape and is secured at its lower end to the reversely bent end of the terminal strip 2I3. The terminal strip 2I3 has a rightangled bend therein and the strip flts snugly in the slot 9| and in a portion of the elongated slot 2M formed in the housing section 3|, as shown in Fig. 8. The terminal end of the terminal strip 2 I3 is provided with a lug (not shown) on one side thereof which fits snugly in the rectangular recess 81 of the housing section 3i in the same manner as the lug 85 of the terminal 29 shown in Fig. 4. The terminal 3 and the bimetal element 2| I carried thereby are fitted into the housing section 8| by sliding the same edgewise into the slots 9| and MI in the position shown in Fig. 8 and are securely retained in mounted positions when the housing sections 3i and 33 are assembled. The free end of the bimetal element III is connected by a flexible shunt conductor II! to the releasable pivoted supporting lever I I3 and is thereby electrically connected in series with the contacts of the breaker so as to be traversed by the current flowing through the circuit controlled by the breaker. Upon overload of the circuit, the bimetal element ZII is heated by the overload current and upon attaining a predetermined temperature the free end thereof deflects downwardly away from the circuit breaker mechanism and effects release of the pivoted supporting lever I33, thereby causing automatic opening of the circuit breaker contacts. After the bimetal has cooled following interruption of the circuit, the free end thereof returns to the normal position shown in Fig. 8 and the breaker may be reset manually by moving the operating handle downwardly to the open position.

An adjusting screw 2 I6 is threaded in an opening provided therefor in the terminal 2I3 and the point of the screw engages the reversely bent end of the terminal as shown in Fig. 8. The screw 2 I8 serves as a means for calibrating and adjusting the trip characteristic of the breaker by changing the amount of overlap of the latch end of the bimetal element with respect to the latch element I2I of the breaker mechanism. When the screw is turned clockwise the reversely bent end of the terminal i moved upwardly, increasing the amount of overlap of the latch, and conversely when the screw is turned counterclockwise, the reversely bent end of the terminal .moves downwardly due to its resiliency and thereby decreases the amount of latch overlap. The screw 2H5 may be adjusted from outside the housing through the opening I12.

The circuit breaker as equipped with a magnetically responsive trip responsive device is shown in Fig. 9. The magnetically responsive trip device is identical in construction to the trip device shown in Figs. 1 through 6, except that the bimetal element is omitted, and a compression spring 2II is substituted in place of the tension spring I68 used in the embodiment of the invention shown in Figs. 1 through 6. Since the magnetically responsive device is identical in construction to the trip device shown and described in connection with the original embodiment with the exceptions noted above, the same reference characters have been used to designate the corresponding parts and it is not believed necessary to again describe the construction. The magnetically responsive trip device is removably fittedin the housing in the same manner as the trip device of the original embodiment, fltting into 14 the same recesses and engaging the same surfaces.

The bracket I1! to which the upper end of the energizing winding I83 of the electromagnet is connected is in turn electrically connected to the releasable support member I I3 by a flexible shunt conductor 2I8, thereby connecting the winding in series with the contacts of the breaker. The latch lever IBI is in this instance biased to latching position by the compression spring 2", and the strength of the spring is adjusted by the screw I13 so that the breaker will be automatically tripped by the electromagnet whenever the current exceeds the predetermined selected value.

A modification of the invention is shown in Fig. 7. This modification of the invention is identical in construction and operation to the embodiment of the invention shown in Figs. 1 through 8 and described in connection therewith except that a resilient element in the form of a spring strip II! of predetermined strength is interposed between the free end of the bimetal element It! and the end of the latch lever Iii. The spring strip 2 I9 is fastened to the lower side of the free end of the bimetal element I55 by means of a rivet HI and the inner end of the strip engages the insulating button I" of the latch lever IUI. When the bimetal element I55 is in the normal position shown in Fig. 7, the spring strip 2 I 9 carried thereby provides a substantially constant force opposing unlatched movement of the latch lever IEI, and the spring strip and bimetal element normally maintain the latch lever in latching position. As the current of the circuit increases beyond the normal rated current, the bimetallic element I55 is heated thereby and the free end thereof gradually deflects downwardly, decreasing the restraining force opposing unlatching until the breaker is finally tripped by the unlatching force of the electromagnet I53 and spring I68. The latch lever Iii is moved to the unlatched position as soon as the combined force of the electromagnet I53 and spring I" is sufficient to overcome the opposing force of the leaf spring 2I9, or as soon as the bimetal element I55 has deflected a sufficient amount to permit unlatching. Upon the occurrence of overload currents in excess of a predetermined value, for example, about 1000% of the rated current, the pull of the electromagnet is sufficient to deflect the leaf spring H9 and cause the release of the latch lever Iii even though the bimetal element I55 may not have been heated a substantial amount. It will thus be seen that the provision of the resilient element or leaf spring 2l9 provides a predetermined and substantially constant force opposing unlatching or tripping of the breaker which is independent of the thickness or stiffness of the bimetal element I55. This enables bimetal elements of different thickness and stiffness to be substituted without changing the instantaneous trip setting of the breaker. In other words the breaker will be tripped instantaneously whenever the current exceeds a predetermined high value, i'or example, 1000% of the rated current irrespective of what the thickness or stiffness of the bimetal element may be.

While the invention has been disclosed in accordance with the provision of the patent statutes, it is to be understood that various changes in the structural details thereof may be made without departing from some of the essential features of the invention. It is desired, therefore. that the language of the appended claims be given the broadest reasonable interpretation permissible in the light of the prior art.

I claim as my invention:

1. A circuit breaker comprising, in combination, relatively movable contacts, operating means therefor operable to open and to close said contacts, a trip device including a bimetal element having a stationary end and a movable end' operable to cause opening of said contacts, terminals for connecting the breaker in an electrical circuit, one of said terminals being connected to the stationary end of the bimetal element by a conductor permitting some relative movement between the terminal and bimetal element, an insulating housing for the aforementioned parts comprising two separable sections having a joint between them, said housing serving as the frame for the breaker and having recesses and projections for supporting said parts without any of said parts being positively fastened to said housing, said parts being removably mounted through the open side of one of said sections at the joint when the sections are separated and being retained in mounted position when the housing sections are assembled and said stationary end of the bimetal element being biased against the housing in a direction to take up any looseness in its mounting which would affect the calibration of the breaker.

2. A circuit breaker comprising, in combination, an open-sided casing of insulating material having covering means for the open side, a stationary contact, a cooperating movable switch member, operating means for moving said switch member to op n and to closed circuit position, a trip device including a bimetal element having a stationary end and a movable end operable to cause movement of said switch member to open circuit position independently of the position of said operating means, terminals for connecting the breaker in an electrical circuit, one of said terminals being connected to the stationary end of the bimetal element by a conductor permitting some relative movement between the terminal and bimetal element, said casing having means for receiving and supporting all of the abovementioned parts whereby all of said parts are removably mounted in said casing through the open side and are retained in mounted position without any fastening devices when the cover is in mounted position on said casing.

3. A circuit breaker comprising, in combination, relatively movable contacts, operating means manually operable to open and to close said contacts, a trip device including a bimetal element having a stationary end and a movable end operable in response to predetermined conditions to cause automatic opening of said contacts, terminals for connecting the breaker in an electrical circuit, one of said terminals being connected to the stationary end of the bimetal element by a conductor permitting some relative movement between the terminal and bimetal element, aninsulating housing for the aforementioned parts comprising two separable members having a joint therebetween, said housing serving as the frame for the breaker and having means of the insulating material of said housing for mounting and directly supporting the stationary end of said bimetal elements and the terminal connected thereto without either-of said last mentioned parts being positively fastened to said housing and said stationary end of the bimetal element being biased against the housing in a direction to take up any looseness in its mounting which would affect the calibration of the breaker.

4. A circuit interrupter comprising circuit making and breaking mechanism including a bimetal element having a stationary end and a movable end, terminals for connecting the interrupter in an electrical circuit, one of said terminals being connected to the stationary end of the bimetal element by a conductor permitting some relative movement between the terminal and bimetal element, an insulating housing for the interrupter comprising two separable members having a Joint between them, at least one of said housing members serving as the frame for the circuit making and breaking mechanism and having means for removably mounting and supporting said mechanism without any part of said mechanism being positively fastened to said housing, said housing member also having recesses and surfaces for engaging and fixedly supporting said terminals without said terminals being positively fastened to said housing, said mechanism and terminals being removably mounted through the open side of said housing member at the joint when said housing members are separated and being securely retained in mounted position when said housing members are assembled.

5. A circuit breaker comprising circuit making and breaking mechanism, a thermally responsive element of bimetallic material operable in response to predetermined conditions to cause a circuit opening operation of said mechanism, an insulating housing for the breaker comprising two separable members having a Joint between them, at least one of said housing members forming the frame of the breaker and having means for supporting said mechanism without any part of said mechanism being positively fastened to said housing, said housing also having one or more recesses and surfaces for receiving and fixedly supporting one end of said bimetal element against movement in all directions except outwardly through the open side, and said housing member slidably receiving said mechanism and bimetal element through its open side at the Joint so that when the housing members are assembled the said parts are securely retained in mounted position without being positively fastened to said housing.

6. A circuit breaker comprising circuit making and breaking mechanism, a thermally responsive element of bimetallic material operable in response to predetermined conditions to cause circuit opening operation of said mechanism, an insulating housing for the breaker comprising two separable members having a joint between them, said housing serving as the frame for the breaker and having means for mounting said mechanism without any part of said mechanism being positively fastened to said housing and having means for fixedly supporting one end of said bimetal element without said element being positively fastened to said housing, said mechanism and said bimetal element being removably mounted in said housing through the open side of one of said housing members at the joint when the members are separated and being retained in mounted position when the housing members are assembled.

'I. A circuit breaker comprising, in combination, contact means and operating means or opening and closing said contact means, an electromagnet energized in response to the current of the circuit operable in response to predetermined conditions to cause automatic opening of said contact means, an insulating housing for the breaker comprising two separable insulating members having a Joint between them, said said contact means and operating means and also having recesses and surfaces for engaging and supporting an element of said electromagnet, said contact means and operating means and said electromagnet being removably mounted in said housing through the open side of one of said housing members at the joint when said housing members are separated and being 58-- curely retained in mounted position when said housing members are assembled without any of said parts being positively fastened to said housing members.

8. A circuit breaker comprising, in combina-- tion, a stationary contact, a cooperating movable switch member, operating means for moving the switch member to open and to closed circuit position, a trip device comprising an electromagnet energized in response to the current of the circult operable in response to predetermined conditions to cause movement of the switch member to open circuit position, terminals for connecting the breaker in an electrical circuit, an insulating housing for the breaker comprising two separable members having a Joint between them, said housing serving as the sole frame for the breaker and being formed to provide recesses and surfaces for receiving and supporting all of the aforementioned parts without any of said parts being positively fastened to said housing members, said aforementioned parts being removably mounted through the open side at the Joint of one of said housing members when the housing members are separated and being retained in mounted position when the housing members are assembled.

9. A circuit breaker comprising, in combination, an open-sided casing of insulating material, a stationary contact, a cooperating movable contact, operating means for opening and closing said contacts, a trip device comprising an electromagnet and a bimetal element energized in response to the current of the circuit and operable in response to predetermined conditions to cause automatic opening of the contacts, terminals for connecting the breaker in an electrical circuit, said casing being formed to provide recesses and surfaces for removably receiving the aforementioned parts through the open side and for supporting said parts, a second casing member for completing the casing and holding the above-mentioned parts in mounted position whereby said parts are retained in mounted position without any of said parts being positively fastened to said casing members.

10. A circuit breaker comprising, in combination, contact means, operating means for opening and closing said contact means including a spring biased member releasable to cause automatic opening of said contact means, a, trip device comprising a current responsive bimetal element normally restraining said spring biased member and operable in response to predetermined conditions to cause release of said member, thereby effecting automatic opening of said contacts, an insulating housing for the breaker comprising two separable sections having a joint between them, said housing serving as the frame of the breaker and being formed to provide recesses and surfaces for receiving and supporting said contact means and operating means without said parts being positively fastened to said housing, and said housing also having additional recesses and surfaces for engaging and fixedly supporting one end of said bimetal element to support the bimetal element in proper position relative to said releasable member without said bimetal element being positively fastened to said housing, said contact means and said operating means and said bimetal element being removably mounted in said housing through the open side of one of said housing members at the joint when said housing members are separated and being retained in mounted position when said housing membersare assembled, said supporting surfaces being disposed so that the reaction forces on said parts cause them to seat against said surfaces in such a, manner that the accuracy of operation of the breaker is substantially unaffected by the degree of looseness of fit of said parts in said housing.

11; A circuit breaker comprising, in combination, contact means, operating means for opening and closing said contact means including a pivoted spring biased member releasable to cause automatic opening of said contact means, a pivoted latch for normally restraining said releasable member, electro-responsive means operable in response to predetermined conditions to cause release of said latch, an insulating casing for the breaker comprising two separable sections having a joint between them, said housing forming the sole frame for the breaker parts and having bearing recesses for the pivots of said releasable member and said latch and having additional recesses and surfaces for supporting the other aforementioned parts without any of said parts being positively fastened to said housing, said parts being removably mounted in said housing through the open side of one of said housing sections when the housing sections are separated and being retained in mounted position when the housing sections are assembled, said parts and the surfaces against which they bear being disposed so that the reaction on said parts cause them to naturally seat against the surfaces in such a manner that the accuracy of operation of the breaker is substantially unaffected by the degree of looseness of fit of said parts in said housing.

12. A circuit breaker comprising relatively movable contacts, operating means for opening and closing said contacts, an electromagnet energized in response to the current of the circuit and operable in response to predetermined conditions to cause automatic opening of said contacts, an insulating housing for the breaker comprising two separable members having a joint between them, at least one of said housing members serving as the frame of the breaker and having means for receiving and for supporting said contacts and operating means without being positively fastened thereto and having recesses and surfaces for receiving and supporting an element of said electromagnet without said electromagnet being positively fastened to said housing.

13. A circuit breaker comprising, in combination, contact means, operating means therefor including a manually operable operating member, a thermally responsive bimetal element fixedly mounted .at one end and operable in response to predeterminedoverload condition to cause automatic opening of the contact means, terminals for connecting the breaker in an electrical circuit, an insulating housing for enclosing all of the aforementioned parts other than the operating end of the manually operable member and the terminal ends of said terminals and comprising two separable members having a joint between them gene y parallel to the plane of movement of said contact means, Sai housing serving as the sole frame for the breaker and having recesses and surfaces for supp ing all of the above-mentioned parts in operative position without any of said parts being positively fastened to said housing, said parts being removably mounted through the open side of one of said housing members at the joint when the housing members are separated and being retained in mounted position therewithin when the housing members are assembled.

14. A circuit breaker comprising, in combination, an open sided casing, contact means, operating means therefor including a manually operable operating member for manually operating said contact means, an electromagnet energized by the current of the circuit operable in response to predetermined conditions to cause automatic opening of said contact means, terminals for connecting the breaker in an electrical circuit, said casing serving as the frame for the breaker and having recesses and surfaces for slidably receiving the aforementioned parts through the open side and for supporting the aforementioned parts, a second casing member for completing the casing and holding all of the above-mentioned parts in mounted position therewithin without any of said parts being positively fastened to said casing members.

15. A circuit breaker comprising, in combination, an open sided casing of insulating material, a stationary contact, a cooperating movable switch member, operating means for said switch member including a manually operable operating member, an actuating spring connecting said operating member and said switch member, a pivoted member releasable to cause movement of said switch member to open circuit position, and a trip device mounted separately from said switch member and releasable member normally restraining said releasable member and operable in response to predetermined condition to effect release of said releasable member, said casing having recesses and surfaces for receiving and supporting the aforementioned parts including a surface forming one bearing for said operating member on one side of said spring, a second casing member removably mounted on the open side of said casing for completing the casing, said second casing member having a bearing surface forming a second bearing for said operating member on the side of the spring opposite the first bearing, all of said parts being removably mounted through the open side of said casing and being retained in mounted position therewithin by said second casing member without any of said parts being positively fastened to said casing members.

16. A circuit breaker comprising, in combination, an open-sided casing of insulating material, a stationary contact, a cooperating movable switch member, operating means for moving the switch member to open and to closed circuit position comprising a manually operable operating lever, an actuating spring connecting said operating lever and said switch member, trip means operable in response to predetermined conditions to cause movement of said switch member to open circuit position irrespective of the position of said operating lever, said casing serving as the frame for the breaker and having recesses and surfaces for supporting the aforementioned parts without being positively fastened thereto, one of said surfaces being formed on the wall of said casing opposite the open side and forming one pivot bearing for engaging and supporting the lever at one side of said actuating spring, said operating lever having a lateral projection adjacent its operating end carrying a rotatable roller on the other side of said actuating spring, a second casing member removably mounted on the open side of said casing for completing the casing and retaining the aforementioned parts therewithin, said second casing member having an arcuate bearing surface engaged by said roller and along which said roller is movable to form a second bearing for the operating lever.

17. A circuit breaker comprising an open-sided casing of insulating material, contact means, operating means for opening and closing said contact means, said casing serving as the frame for the breaker and having recesses and surfaces for receiving and supporting said parts and having additional recesses and surfaces disposed for receiving and supporting a combined magnetically and thermally responsive trip device comprising an electromagnet and a bimetal element, and for receiving and supporting a thermally responsive trip device comprising a bimetal trip element when said magnetically and thermally responsive trip device is removed, and for receiving and supporting a magnetically responsive trip device comprising an electromagnet in place of either of the other trip devices, a closure member removably mounted on the open side of said casing for completing the casing and for retaining said contact means and operating means and whichever trip device is inserted all in mounted position in said casing, said parts being removably mounted in the casing through the open side and retained in mounted position by the closure member without any of said parts being positively fastened to said casing and closure member.

18. A manually and automatically operable circuit breaker comprising an open-sided casing of insulating material, contact means, operating means for opening and closing said contact means, said casing serving as the frame for the breaker and having recesses and surfaces for receiving and supporting said contact means and operating means and having additional recesses and surfaces for receiving and supporting a combined magnetically and thermally responsive trip device comprising an electromagnet and a current responsive bimetal element for tripping said breaker in response to predetermined conditions, and for receiving a thermally responsive trip device comprising a current responsive bimetal trip element when said other trip device is removed, a closure member removably mounted on the open side of said casing for completing the casing and for retaining said contact means and said operating means and whichever trip device is inserted all in mounted position in said casing without any of said parts being positively fastened to said casing or closure member.

19. A manually and automatically operable circuit breaker comprising an open-sided casing of insulating material, contact means, operating means for opening and closing said contact means, said casing serving as the frame for the breaker and having recesses and surfaces for receiving and supporting said contact means and operating means and having additional recesses for receiving and supporting a magnetically responsive trip device comprising an electromagnet for tripping said breaker in response to predetermined conditions, and for receiving and supporting a thermally responsive trip device comprising a current responsive bimetal trip element when said magnetically responsive trip device is removed, a second casing member removably mounted on the open side of the casing for completing the casing and retaining said contact means and operating means and whichever trip device is inserted all in mounted position within said casing, said parts being removably mounted through the open side of the casing and retained in mounted position without any of said parts being positively fastened to said casing members.

20. A circuit breaker comprising, in combina tion, contact means, operating means for openlng and closing said contact means including a pivoted spring biased member releasable to cause automatic openingof said contact means,

an electroresponsive latch operable in response to predetermined conditions to cause release of said releasable member, an insulating casing for the breaker comprising two separable sections having a joint between them, said housing forming a frame and having separate bearing surfaces for the pivot of said releasable member and for said latch without either said releasable member or said latch being positively fastenedto said housing, said releasable member and said latch being removably mounted in said housing through the open side of one of said housing sections when the housing sections are separated and being retained in mounted position when the housing sections are assembled, said releasable member and said latch being biased against their bearings and said surfaces being shaped so that the bias on said parts cause them to naturally seat in a certain position. against their bearing surfaces in such a manner that there is a fixed overlap between said releasable member and said latch under any given electroresponsive condi tion and the accuracy of operation of the breaker is substantially unaffected by the degree of looseness of fit of said parts in said housing.

21. A circuit breaker comprising contact means, operating means for opening and closing said contact means including a pivoted spring biased member releasable to cause automatic opening of said contact means, an electroresponsive latch engageable with said releasable member and pivoted about an axis parallel to the pivot axis of the releasable member, said latch being operable in response to predetermined conditions to release said member, an insulating casing for the breaker comprising two separable sections having a joint between them, said casing forming a frame and having separate generally cylindrical bearing surfaces for the pivots of said releasable member and latch without either said releasable member or said latch being positively fastened to said casing, said releasable member and said latch being removably mounted in'said casing through the open side of one of said sections when the sections are separated and being retained in mounted position when the sections are assembled, and said releasable member and latch in the latched position being biased against their bearings so that the pressure on the pivot bearing of the releasable member is in the same direction and parallel to the pressure on the pivot bearing of the latch thereby maintaining a fixed overlap between the latch and the releasable member under any given electroresponsive condition and maintaining the accuracy of operation of the breaker irrespective of the looseness of fit of said parts in said casing.

22. A circuit interrupter comprising contact means, operating means for opening and closing said contact means including a manually operable operating member having a handle portion, an insulating housing for enclosing the parts of the circuit interrupter except the handle portion of said operating member, said housing comprising two separable sections having a joint therebetween, portions of said housing sections overlapping one another in spaced relation to provide a slot through which a portion of said operating member extends and said last mentioned portion of the operating member being bent to extend parallel to and between the opposed surfaces of the overlapped portions of said housing sections.

23. A circuit interrupter comprising contact means, operating means for opening and closing said contact means including a manually operable operating member having a handle portion, an insulating housing for enclosing the parts of the circuit interrupter except the handle portion of said operating member, said housing comprising two separable sections having a joint therebetween extending in a direction generally parallel to the plane of movement of said handle portion, portions of said housing sections overlapping one another in spaced relation to provide a slot extending at substantially a right angle to said plane of movement and through which a portion of said operating member extends and said last mentioned portion of the operating member extending substantially parallel to and between the opposed surfaces of the overlapped portions of said housing" sections.

24. A circuit breaker comprising, in combination, contact means, operating means for said contact means including a spring biased member releasable to cause automatic opening of said contact means, a magnetic pole piece, an armature pivoted thereon and having a latch portion normally in latching engagement with said spring biased member but releasing it upon the occurrence of an abnormal condition, a housing for the circuit breaker including a housing section of in sulating material having recesses for supporting said parts without any of said parts being fastened to said housing, and the pivot of said armature extending into said pole piece and into the insulating material of the housing section for accurately positioning said latch portion in position to engage said spring biased member.

25. A circuit breaker comprising, in combination, contact means, operating means for said contact means including a pivoted spring biased member releasable to cause automatic opening of said contact means, a magnetic pole piece, an armature pivoted thereon and having a latch portion normally in latching engagement with said spring biased member but releasing it upon the occurrence of an abnormal condition, a housing for the circuit breaker including a housing section of insulating material, the pivot of said spring biased member engaging a bearing surface on said insulating material and the pivot of said armature on said pole piece also engaging a hearing surface on said insulating material, and each of said pivots being biased against its bearing surface and said surfaces being shaped so that the bias on the pivots causes them to seat in a certain position and provide a definite latching relation between said spring biased member and the latch portion of the armature.

' OLIVER S. JENNINGS.

(References on following page) The following references are of record in the REFERENCES CITED file of this patent:

UNITED STATES PATENTS Number Name Date Dorfman Aug. 11, 1936 Number